Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical) - $ / shares shares in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Common stock per share dividend amount	$ 2.55	$ 2.25
Retained Earnings [Member]
Common stock per share dividend amount	$ 2.55	$ 2.25
Series A Warrants [Member] \| Treasury Stock [Member]
Exercise of warrants into shares of common stock	76,517	304,436
Exercise of warrants into shares of common stock	45,426	165,498

Number of shares issued during the period as a result of the conversion of convertible securities.

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